1. Field of Invention
This invention relates to methods of making steel and more particularly methods of operating a blast furnace.
2. Prior Art
In a blast furnace, counter current reactions are conducted between the mixture of solids, liquids and gasses contained in the blast furnace, the mixture descending from top to bottom and the gases ascending from bottom to top. Therefore, in order to favorably operate the blast furnace, it is necessary to keep the physical and chemical conditions of the gases, solids and liquids (hereinafter referred to as the furnace condition) stable in some desirable manner. Included in the disturbing factors governing the furnace condition are many factors such as the properties of the charge covering the reducability, strength, noncollapsability, chemical components, grain size, and the flow rate of the hot air, temperature of the hot air, temperature of the deposits on the refractory wall of the furnace, damage to the blast furnace cooling system, in-furnace storage level of molten materials such as molten metal and molten slag and the like.
Blast furnace operators constantly observe the changes in the disturbing factors to timely control the or/coke, flow rate of hot air, temperature of hot air and other controllable factors to appropriate values thereby enabling them to keep furnace conditions stable.
However, even if variations of the variable factors are observed, it is difficult to effect an optimum control of the controllable factors to keep the furnace condition stable. This is a result of: (1) variations in the disturbing factors in most cases is unpredicatble, (2) the magnitude of the variations can be only quantatitively observed and (3) the influence of the variations on the furnace condition is complicated by the influence of other disturbing factors thereon. For these reasons, there has been practiced such a furnace control method in general that the blast furnace operators observe the changes in the disturbing factors and at the same time observe the changes in the furnace condition resulting from the disturbing factors and the furnace conditions indicative factors indicating the current furnace condition so as to effect the fine adjustment on these controllable factors to thereby try to bring the changes of the furnace condition indicative factors to a better condition. On the other hand, there are many furnace control indicative factors and the changes of the individual factors are complicated by one another as a result of variations in relative lag time due to the patterns of the furnace condition. Hence, it has been difficult for the blast furnace operators to determine the pattern of furnace conditions based on their observance of the furnace condition indicative factors. For this reason, a standard method of grasping the furnace condition has been determined by a series of technical knowhow and the blast furnace operators have been determining the furnace condition based on their understanding of the standardized reference. Although the flow of thought in which the reference is standardized has been defined, the abilities and experience of the individual operators of the blast furnace is reflected in the results of their judgement on the furnace condition and there has been generally such a difference in skill in grasping the furnace condition from person to person since there are so many furnace condition factors and the types of changes are very complicated.